US9319240B2 - Ethernet Ring Protection node - Google Patents
Ethernet Ring Protection node Download PDFInfo
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- US9319240B2 US9319240B2 US14/035,035 US201314035035A US9319240B2 US 9319240 B2 US9319240 B2 US 9319240B2 US 201314035035 A US201314035035 A US 201314035035A US 9319240 B2 US9319240 B2 US 9319240B2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
- H04L12/437—Ring fault isolation or reconfiguration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40169—Flexible bus arrangements
- H04L12/40176—Flexible bus arrangements involving redundancy
- H04L12/40195—Flexible bus arrangements involving redundancy by using a plurality of nodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/06—Management of faults, events, alarms or notifications
- H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
- H04L41/0668—Management of faults, events, alarms or notifications using network fault recovery by dynamic selection of recovery network elements, e.g. replacement by the most appropriate element after failure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/18—Loop-free operations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/22—Alternate routing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/28—Routing or path finding of packets in data switching networks using route fault recovery
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/06—Management of faults, events, alarms or notifications
- H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
- H04L41/0659—Management of faults, events, alarms or notifications using network fault recovery by isolating or reconfiguring faulty entities
- H04L41/0661—Management of faults, events, alarms or notifications using network fault recovery by isolating or reconfiguring faulty entities by reconfiguring faulty entities
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- H04L41/0672—
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/08—Configuration management of networks or network elements
- H04L41/0803—Configuration setting
- H04L41/0813—Configuration setting characterised by the conditions triggering a change of settings
- H04L41/0816—Configuration setting characterised by the conditions triggering a change of settings the condition being an adaptation, e.g. in response to network events
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L43/00—Arrangements for monitoring or testing data switching networks
- H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
- H04L43/0805—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability
- H04L43/0811—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters by checking availability by checking connectivity
Definitions
- This invention relates to network nodes and more particularly to systems and methods for nodes supporting data-link-layer, ring-protection-switching protocols.
- switching protection protocols such as the Spanning Tree Protocol (STP)
- STP Spanning Tree Protocol
- MAC Media Access Control
- Ethernet Ring Protection (ERP) protocols such as the ERP protocol defined in International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) G. 8032, provide examples of switch protection protocols with dramatically improved recovery times.
- ITU-T International Telecommunication Union-Telecommunication Standardization Sector
- a node supporting an ERP may have more than two ports into/out of the node, the node can satisfy the ring architecture of an ERP ring by connecting to one or more additional nodes within an ERP ring with two ring ports. Additional ports may connect a node participating in the ring to nodes outside of the ring. Since a ring, by definition results in a loop, ERPs may block a link between a designated pair of nodes to prevent such loops. Despite the blocked link between two nodes, all of the nodes in the ring can still communicate with one another by passing information along the remaining backbone of serviceable links in one direction or another, depending on which is shortest.
- the blocked link can be unblocked, since the failure prevents loops by effectively blocking a new link at a new location. Since the previously blocked link is now unblocked, all the nodes in the ring can still communicate with each other across a new backbone of serviceable links, although the directions in which communications are sent and from which they are received may change do to a new location of a new blocked link.
- FIG. 1 is a schematic block diagram of a network including a ring architecture on which a ring protection protocol is implemented in accordance with an embodiment of the present invention
- FIG. 2 a is a schematic block diagram of ring node implementing a single, ring-protection state machine in accordance with prior art
- FIG. 2 b is a schematic block diagram of a ring node whose two ring ports are each maintained by a separate line card with its own ring-protection state machine, in accordance with an embodiment of the present invention
- FIG. 3 is a schematic block diagram of a ring node within a ring implementing a ring protection protocol where one of the ring node's ring ports has failed, but which still provides access to nodes external to the ring through the remaining ring port under the control of a surviving state machine, in accordance with an embodiment of the present invention
- FIG. 4 is a schematic block diagram of a backplane providing communication infrastructure between line cards residing at a common ring node and between two state machines on two such line cards, in accordance with an embodiment of the present invention
- FIG. 5 is a schematic block diagram of two state machines at the physical plane becoming transparent at the management plane for seamless interfaces with third-party devices implementing a ring protection protocol, in accordance with an embodiment of the present invention
- FIG. 6 is a schematic block diagram of a line card maintaining a front port capable of serving as a ring port and a virtual port, with details about switch infrastructure on the line card and a switch protection module with a state machine used to implement a ring protection protocol, in accordance with an embodiment of the present invention
- FIG. 7 is a sequence diagram of interactions between a pair of slots on a ring node, each with a front port serving as a ring port, a virtual port, and a state machine to, among other things, (1) synchronize the state machines, (2) respond to failures on a link used to synchronize the state machines, and (3) prevent a loop when the link recovers, in accordance with an embodiment of the present invention;
- FIG. 8 is a schematic block diagram of a system progression for (1) a ring architecture implementing a ring protection protocol with a ring node experiencing a failure on an internal link between two state machines, progressing to (2) the ring node blocking a ring port to prevent a loop as the ring protection link for the ring is unblocked, and progressing to (3) the ring node unblocking the ring port after the ring protection link is blocked again, in accordance with an embodiment of the present invention;
- FIG. 9 is a flow chart of a method for determining whether to respond to a message with a node identification value matching that of a line card/slot receiving the message in an environment where the two ports of a ring node are maintained by two line cards/slots with a common node identification value, in accordance with an embodiment of the present invention.
- FIG. 10 is a flow chart of a method for (1) responding to failures on a link between multiple state machines at a common ring node and (2) preventing a loop after the previously failed link is recovered, in accordance with an embodiment of the present invention.
- ring-protection protocols such as Ethernet Ring Protection (ERP) protocols may prevent loops, provide greatly improved recovery times in response to network failures, and provide redundancy across their ring architecture by the potential to unblock a ring protection link ordinarily blocked in a default position. Additional redundancy, however, may be provided at the level of individual nodes in the ring architecture.
- a node participating in a ring architecture may also be networked to large portions of a network external to the ring-architecture portion of the network. The connectivity provided by such a node may be lost where the node fails in the absence of redundancy at the node level to maintain this connectivity.
- node-level redundancy may include more than redundant connections, but may also include redundancies of one or more elements implementing the ring protection protocol, such as state machines. Also, to preserve the protection against loops provided by ring protection protocols, the details implementing node-level redundancy may include measures to prevent loops despite any changes arising from the implementation of node-level redundancies. Additionally, to facilitate integration of such a node into a ring of nodes implementing the ring protection protocol, ideally, details of such redundancies would be transparent at the node level.
- a non-limiting, exemplary embodiment may involve implementing a ring-protection-protocol state machine on each of two different line cards residing at a common ring node.
- a front port of each line card may provide/maintain one ring port of the two ring ports defined for a ring node by the ring protection protocol. Therefore, if one ring card and/or state machine goes dark a surviving state machine may provide redundant connectivity, and a surviving state machine may provide redundant implementation of the ring protection protocol at the node.
- the multiple state machines may be synchronized as one logical state machine.
- the first ring-protection-protocol state machine on a first line card of the two line cards may be updated to an updated state.
- a message may then be passed from a first virtual port of the first line card over a backplane of the ring node to a second virtual port of the second line card.
- the second ring-protection-protocol state machine on the second line card of the two line cards may then also be updated to the updated state in response to the message received at the second virtual port.
- the first state machine and the second state machine are synchronized as a common virtual state machine with respect to the ring node.
- Messages used generally by the ring protection protocol to update the state of nodes in a ring implementing the ring protection protocol may be passed over the backplane to also synchronize multiple state machines at a common node providing the backplane.
- This backplane link may be monitored for failure.
- a failure may be addressed with messages used to respond to general ring failures.
- different roles may be assigned to the different state machines to respond to a recovery of the previously-failed backplane link between the state machines to prevent a loop. For example, while a ring protection link may remain unblocked in response to failure messages sent in response to the failure of the backplane link, one state machine may be assigned to block one of the ring ports of the redundant node to prevent a loop. This ring port may not be unblocked until an indication is received that the ring protection link is again blocked, according to the rings default posture, to prevent another potential loop.
- state machines may be modified to respond to messages even though the messages may have a common identification node value, indicative that the message may have run their course and may be returning to their originator. State machines may be modified to respond to such matching messages where such messages are received over a virtual port, as opposed to a ring port, indicative of the messages originating with a paired sate machine and containing synchronization information. Further details of approaches to achieving node-level redundancy can be informed by networking and ring protection protocol considerations discussed below with respect to FIG. 1 .
- a ring architecture 10 is depicted with multiple nodes 12 a - f participating in the ring architecture 10 .
- Additional nodes 12 g - k may participate in a network with the multiple nodes 12 a - f of the ring architecture 10 .
- the network can be a data-layer network (layer 2 of the Open Systems Interconnection (OSI) model), such as, but not necessarily, an Ethernet network.
- OSI Open Systems Interconnection
- individual nodes may be instances of various forms of switches 12 c .
- Such switches may be classified according to different categories. For example, a group of switches 12 may be categorized as access switches 12 . Another group may be categorized as aggregation switches 12 .
- Nodes 12 may be connected one to another by links 14 a - k .
- links 14 a - f between nodes 12 a - 12 f in the ring 10 may be Network-to-Network Interfaces (NNI).
- the links 14 a - k used to form the ring architecture 10 may be bi-directional links.
- the links 14 g - k between a node 12 f participating in the ring 10 and nodes outside of the ring 12 g - k may include one or more NNIs and/or User-to-Network Interfaces (UNIs).
- the multiple nodes 12 a - f in the ring 10 may implement a ring protection protocol, such as an ERP protocol.
- a ring protection protocol such as an ERP protocol.
- the ring 10 is made up of six nodes 12 a - f in FIG. 1 , many different numbers of nodes 12 may be involved.
- One, non-limiting example of a ring protection protocol may be found in ITU-T G.8032, but other ring protection protocols are possible.
- the ring structure 10 resulting from the six links 14 a - f between the six nodes 12 a - f can provide redundancy.
- the ring structure 10 may also result in a problematic loop.
- a ring protection protocol may designate a particular link 14 a as a Ring Protection Link (RPL) 14 a .
- RPL Ring Protection Link
- the first 12 a and the second nodes 12 b may maintain the RPL 14 a
- the first 12 a and the second nodes 12 b may also block 16 a , 16 b the RPL 14 a to prevent a loop from forming within the ring 10 .
- redundancy may be preserved.
- By blocking 16 the RPL 14 a a loop can be prevented.
- the first 12 a and the second nodes 12 b may remove the blocks 16 a , 16 b to the RPL 14 a .
- any node 12 a - f on the ring 10 can still be accessed across a C-shaped backbone even though one of the remaining links 14 b - f is temporarily down.
- the first 12 a and the second nodes 12 b may again block 16 a , 16 b the RPL 14 a to prevent a loop.
- the ring protection protocol may designate one node 12 a as an Owner RPL (ORPL) node 12 a .
- ORPL Owner RPL
- FIG. 1 the ORPL node 12 a is indicated by the bold border outline. Specific functions related to blocking 16 a and unblocking and/or initiating the blocking 16 and/or unblocking of the RPL 14 a may be assigned and performed on the basis of a node's 12 a status as an ORPL node 12 a.
- specific functions related to blocking 16 b and unblocking and/or coordinating the blocking 16 and unblocking of the RPL 14 a may be assigned and performed on the basis of a node's 12 b status as an RPL-neighbor node 12 b .
- an example RPL-neighbor node 12 b is indicated by the double-lined border outline. Therefore, in some examples, implementation of a ring protection protocol may involve referencing a position of a node 12 relative to the RPL 14 a in the ring 10 .
- two ring ports 18 a , 18 b may be defined for ring nodes 12 a - 12 f supporting the ring protection protocol.
- One ring port may be referred to as a west port 18 a
- another ring port may be referred to as an east port 18 b .
- the west port 18 a and the east port 18 b of each node 12 a - f are sufficient to link the nodes 12 a - f together in a ring structure 10 .
- Additional ports may connect a ring node 12 f to client nodes 12 g - k external to the ring 10 .
- a ring node 12 d - 1 is provisioned with a single line card 20 a .
- the line card 20 a may have at least two front ports 22 a , 22 b .
- the line card 20 a may maintain the west port 18 a of the ring node 12 d - 1 over the first front port 22 a and the east port 18 b over the second front port 22 b .
- a state machine 24 a may reside on the line card 20 a .
- the state machine 20 a may increment its state in response to one or more messages about relevant events occurring in the ring 10 received over the west port 18 a and/or the east port 18 b and/or events occurring locally with respect to the ring node 12 d - 1 .
- the term ‘line card’ can refer to hardware commonly referred to as a line card, but may also refer to other forms of infrastructure capable of maintaining a ring port 18 and/or a state machine 24 and vice versa.
- the state machine 24 a may perform such state-dependent actions as sending and responding to messages to coordinate implementation of the ring protection protocol. Additional actions may include blocking 16 and unblocking ports to prevent loops and insure that communication between nodes 12 a - f in the ring 10 is preserved. The state machine 24 a may also perform additional actions related to the implementation of the ring protection protocol.
- the ring node 12 d - 2 may include two line cards 20 b , 20 c , as opposed to the single line card in FIG. 2 a .
- the first line card 20 b and the second line card 20 c may be used to implement the ring node 12 d - 2 .
- the first line card 20 b may include a first front port 22 c and a first state machine 24 b .
- the second line card 20 d may include a second front port 22 d and a second state machine 24 c .
- the depiction of two line cards 20 and two state machines 24 does not limit the principles discussed herein from being applied to ring nodes 12 with greater numbers of line cards and/or state machines 24 , as indicated by the use of such terms as ‘multiple state machines.’
- each ring port 18 c , 18 d may be maintained by a separate line card 20 b , 20 c .
- the first front port 22 c of the first line card 20 b may serve as the first ring port 18 c .
- the second front port 22 d of the second line card 20 c may serve as the second ring port 18 d .
- the first line card 20 b , first front port 22 c , and first state machine 24 b may be associated with the west port 18 a
- the second line card 20 c , second front port 22 d , and second state machine 24 c may be associated with the east port 18 b .
- these assignments may be reversed for purposes of interpreting the claims.
- the first state machine 24 b and/or the second state machine 24 c may implement state machines consistent with a ring protection protocol, such as an ERP protocol. Since a separate line card 20 b / 20 c maintains each of the individual ports 18 c / 18 d , if one of the two line cards 20 b , 20 c goes dark, or fails, in part or entirely, traffic on the ring 10 may be redirected to the ring node 12 d - 2 through the remaining line card 20 b / 20 c .
- a ring protection protocol such as an ERP protocol
- this redundancy not only provides node-level redundancy in terms of the ring node's participation in the ring 10 , but also in terms of the connections between the ring 10 and external client nodes 12 g - k through the ring node 12 d - 2 .
- a ring architecture 10 is depicted with a ring node 12 d - 2 implemented using redundant line cards 20 b , 20 c and redundant state machines 24 b , 24 c similar to the ring node 12 d - 2 depicted in FIG. 2 b .
- one of the line cards 20 c has gone dark, or failed 26 , causing the east ring port 18 d to fail. Consequently, the fourth link 14 d between the fourth line card 12 d and the fifth line card 12 e goes down 28 .
- the fourth ring node 12 d and/or the fifth ring node 12 e may send out a failure message 30 a , 30 b over the third link 14 c and/or the fifth link 14 e .
- the failure message(s) 30 a , 30 b may be relayed to an ORPL node 12 a and/or RPL-neighbor node 12 b which can respond to the failure message(s) 30 a , 30 b by unblocking 32 a , 32 b the RPL 14 a .
- the unblocking 32 a , 32 b of the RPL 14 a may be coordinated by an ORPL node 12 a .
- the failure message(s) 30 a , 30 b may be one or more Ring-Automatic Protection Switching (R-APS) Signal Failure (SF) messages, or R-APS(SF) messages.
- R-APS Ring-Automatic Protection Switching
- SF Ring-Automatic Protection Switching
- the failure message(s) 30 a , 30 b may be repeated periodically while the fourth link 14 d remains down.
- any node 12 a - f in the ring 10 may communicate with any other node 12 a - f in the ring 10 despite the failure 28 that makes the fourth link 14 d unusable.
- the additional line card 20 b used to maintain the west ring port 18 c may allow traffic to continue between the ring 10 and external client nodes 12 m - 12 p with additional links 14 m - p to the ring node 12 d - 2 at which one of the line cards 20 c has gone dark 26 .
- traffic previously passing through a ring port 18 c of the ring node 12 d - 2 maintained by a failed line card 20 c may be redirected to pass through a remaining ring port 18 c of the two ring ports 18 b , 18 c defined for the ring node 12 d - 2 .
- the remaining ring port 18 c may be maintained by the surviving line card 20 b .
- the redirected traffic may then pass across the backplane of the ring node 12 d - 2 and out one or more additional front ports of the ring node 12 d - 2 to one or more client nodes 12 m - p external to the ring of nodes 12 a - f to which the ring node 12 d - 2 pertains.
- the surviving state machine 24 b may insure that the ring node 12 d - 2 and the traffic surviving thereon proceeds under ring protection control provided by the surviving state machine 24 b residing on the surviving line card 20 b .
- traffic may also flow from one or more external client nodes 12 m - p to the ring 10 across the ring node 12 d - 2 in the opposite direction.
- the discussions about a failure 26 at a line card 20 c maintaining the east ring port 18 d are equally applicable to a scenario where the failure 26 occurs at a line card 20 b maintaining the west ring port 18 c.
- node-level redundancy may be achieved for traffic at the node 12 d - 2 and ring-protection-protocol controls at that line card 20 . Additional details about how traffic may be passed from a surviving ring port 18 c to one or more external client nodes 12 m - p is provided with respect to FIG. 4 . Additionally, with respect to FIG. 4 a consideration begins of approaches to addressing the implications of introducing a second state machine 24 to a single ring node 12 d - 2 .
- a ring node 12 d - 2 is depicted with multiple line cards 20 b - n and a backplane 34 .
- the backplane 34 may provide communication infrastructure between multiple line cards 20 b - 20 n residing at the ring node 12 d - 2 .
- a backplane 34 may be switch fabric.
- the switch fabric may be implemented with any number of switch-fabric architectures, from a crossbar, switch-fabric architecture to a shared-memory, switch-fabric architecture.
- FIG. 4 depicts ten line cards 20 b - n , as can be appreciated, any number of line cards 20 are possible. Also, although the backplane 34 in FIG. 4 shows interconnections between all line cards 20 b - n , in some examples, the backplane may support communications for a subset of the line cards 20 .
- the ring node 12 d - 2 may include a first state machine 24 b residing on a first line card 20 b , or infrastructure 20 b , maintaining a first ring port 18 c , of two ring ports 18 defined for a layer-two, ring-protection protocol, in terms of a first front port 22 c on that first line card 20 b .
- the ring node 12 d - 2 may include a second state machine 24 c residing on a second line card 20 c , or infrastructure 20 c , maintaining the second ring port 18 d in terms of a second front port 22 d on that second line card 20 c . As depicted in FIG.
- one or more additional line cards 20 d - n may also reside at the ring node 12 d - 2 .
- These additional line cards 20 d - n may have one or more additional front ports 22 d - f linked to one or more client nodes 12 m - p outside of the ring to which the ring node 12 d - 2 belongs.
- a switch-fabric, or switch-fabric like implementation of the backplane may allow any of the line cards 20 b - n residing on the ring node 12 d - 2 to carry linked state machines 24 .
- the one or more additional front ports 22 d - f may be communicatively coupled to both the first line card 20 b and the second line card 20 c over the backlink 34 . Because the backplane 34 can facilitate communication between either the line card 20 b maintaining the west ring port 18 b and/or the line card 20 c maintaining the east ring port 18 c and the additional line cards 20 h , 20 k port 18 b and the additional front ports 22 d - f linked to client node(s) 12 m - p outside of the ring 10 , traffic to and from these client nodes 12 m - p may be maintained if a line card 20 maintaining one ring port 18 is lost. Additionally, although not depicted in FIG.
- any line card 20 with front ports 22 serving as both a ring port 18 and a port 22 connected to client nodes 12 external to the ring 10 may continue to facilitate traffic with the external, client nodes 12 even when the other line card 20 connected to the other ring port 18 fails.
- one or more additional ports 22 d - f may be communicatively coupled to the first ring port 18 c and/or the second ring port 18 d over the backplane 34 and also linked to one or more client nodes 12 m - p outside of the ring 10 of nodes 12 a - f participating in the layer-two, ring-protection protocol.
- including multiple state machines 24 on different line cards 20 at a single node 12 may insure that the node 12 may still be relied upon to implement a ring protection protocol for the ring 10 in which the ring node 12 participates after one state machine 24 fails with the line card 20 on which it resides.
- ring protection protocols rely on state machines 24 implemented at individual nodes 12 a - f to coordinate and implement ring protection protocols, including multiple state machines 24 b , 24 c at a single node 12 d - 2 may result in complications for the ring protection protocol.
- nodes 12 c , 12 e adjacent to the node 12 d - 2 operating the two state machines 24 b , 24 b may interact with that ring node 12 d - 2 as though that ring node 12 d - 2 ran a single state machine 24 , which may result in problems, such as, for example, the possibility of loop generation.
- a ring node 12 d - 2 is depicted that, at the physical plane 36 , implements multiple state machines 24 b , 24 c , which, at the management plane 38 , may be conflated to a single common, or virtual, state machine 40 .
- An inter-card communication link 42 or intra-node link 42 , may be implemented over the backplane 34 between a first virtual port 44 a at the first line card 20 b and a second virtual port 44 b at the second line card 20 c .
- the intra-node link 42 supported by the backplane 34 , may be designed to provide a unit of state information to the first state machine 24 b and the second state machine 24 c so that the first state machine 24 b and the second state machine 24 c can maintain a common state.
- the multiple state machines 24 b , 24 c may logically be conflated to a single, common, virtual state machine 40 . Because the multiple state machines 24 b , 24 c may logically be conflated, they may become transparent at the management plane 38 . Therefore, a network administrator 46 may be provided with an interface to deal with the ring node 12 d - 2 with multiple state machines 24 b , 24 c in the same way as other nodes 12 a - c , 12 e - f in the ring 10 , without any additional rules or considerations.
- the multiple state machines 24 b , 24 c may become transparent to other nodes 12 , including adjacent nodes 12 c , 12 e , in the ring 10 , other nodes 12 may interact with the ring node 12 d - 2 without making provision for additional considerations. Therefore, one or more of the adjacent nodes 12 c , 12 e , may be legacy or third-party devices as long as the adjacent nodes 12 c , 12 e also implement the ring protection protocol of the ring 10 . Additional details about implementation of a virtual port 44 are discussed with respect to the following figure, together with modules that may be used to synchronize multiple state machines 24 and avoid potential loops that the multiple state machines 24 may engender.
- a line card 20 with a front port 22 and a virtual port 44 is depicted.
- the front port 22 and the virtual port 44 can be connected one to another by switch infrastructure 48 .
- the switching infrastructure 48 may perform the switching functions for the line card 20 .
- such operations may include interfacing with the network, interfacing with the backplane 34 , or switch fabric, packet processing, and/or traffic management.
- Receiving and transmitting messages used to coordinate the implementation of a ring protection protocol within a data-layer network may be accomplished with a network interface 50 for one or more front ports 22 and/or a fabric interface 52 for one or more virtual ports 44 .
- Message, packet, and/or frame, processing may be accomplished, in some embodiments, by means of a separate ingress processor 54 and egress processor 56 , which may further be subdivided in terms of transmit and receive operations.
- the ingress processor 54 may inspect a message as it would data packets/frames and determine a destination MAC address of the message.
- the egress processor 56 may encapsulate a message generated at the line card 20 for distribution. Either the ingress processor 54 , the egress processor 56 , or both may be associated with a buffer.
- the switching infrastructure 48 may include a traffic manager 58 to direct a message.
- the traffic manager 58 may include memory storing a database 60 , or switch database 60 , with learned entries associating different destination MAC addresses with different ports.
- the database, or switch database 60 with learned entries may store a switch table, MAC table, Content Addressable Memory (CAM) table, or the like.
- the traffic manager 58 may include one or more counters/timers 62 and a scheduler, used to schedule placement of messages on different ports through the network interface 50 and/or the fabric interface 52 .
- the switch infrastructure 48 may be implemented on multiple chips or on a single chip.
- the line card 20 may include a Central Processing Unit (CPU) 70 , a bus 72 , such as a Peripheral Component Interconnect Express (PCIe) bus, and a switch protection module 74 .
- the switch protection module 74 may provide infrastructure to implement a ring protection protocol. The functions involved in implementing such a ring protection module may be handled by one or more subsets of modules.
- aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.), or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “module.”
- aspects of the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer-usable program code embodied in the medium.
- a computer-readable medium may include one or more of a portable computer diskette, a hard disk, a random access memory (RAM) device, a read-only memory (ROM) device, an erasable programmable read-only memory (EPROM or Flash memory) device, a portable compact disc read-only memory (CDROM), an optical storage device, and a magnetic storage device.
- a computer-readable medium may comprise any non-transitory medium that may contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
- Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++, or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages.
- object-oriented programming language such as Java, Smalltalk, C++, or the like
- conventional procedural programming languages such as the “C” programming language or similar programming languages.
- Any hardware aspects of the switch protection module 74 may be implemented to interact directly with the switch protection module 74 and/or ports 22 , 44 .
- the switch protection module 74 may include a state machine 24 .
- the state machine 24 may subsume the switch protection module 74 .
- the switch protection module 74 may embody additional functionalities and or modules.
- a state machine 24 and/or a switch protection module 74 may include an update module 76 , and internal-blocking module 78 , a messaging module 80 , a master module 82 , a slave module 84 , and/or a preservation module 86 .
- any of the modules may be considered as belonging to a state machine 24 , outside the state machine 24 while within a switch protection module 74 , or partially within a state machine 24 and partially outside a state machine 24 , but within the switch protection module 74 .
- the switch protection module 74 may also include a monitoring module 88 and/or a forwarding module 90 , which also may be considered as belonging in whole or in part to a state machine 24 .
- a forwarding module 90 may be implemented entirely by the switch infrastructure 48 .
- a master module 82 may be mutually exclusive of a slave module 84 for a single state machine 24 , switch protection module 74 , and/or line card 20 and vice versa.
- a master module 82 may address, perform, or coordinate a set of master-role actions 82 explained below by itself or with other modules and/or functionalities.
- a slave module 84 may address, perform, or coordinate a set of slave-role actions 84 explained below by itself or with other modules and/or functionalities. Examples of ways in which master 82 or slave modules 84 , together with additional modules discussed above may be used to make multiple state machines 24 transparent and prevent potential loops that the multiple state machines 24 might generate are discussed with respect to the following figures.
- a series of interactions are depicted between a pair of slots 92 a , 92 b at a ring node 12 d - 2 to (1) synchronize multiple state machines 24 over an inter-card/intra-node link 42 a .
- the interactions may also facilitate a (2) response to a failure 100 on the inter-card link 42 a , coordinating the unblocking 32 of an RPL 14 a , and may (3) prevent a loop from forming upon repair/recovery 108 of the inter-card link 42 a until the RPL 14 a can be blocked 16 again.
- these interactions are presented sequentially, there may be variations in the order of some actions.
- a ring node 12 d - 2 may include a physical chassis with multiple slots 92 , where a slot may receive a line card 20 , or control card, for integration into the implementation of the node 12 d - 2 .
- Each slot 92 may be assigned a letter or number value.
- a chassis may have sixteen slots 92 (any number of two or more slots 92 are possible) with two slots 92 reserved for control cards and fourteen slots 92 reserved for line cards 20 .
- Slot m 92 a and slot n 92 b as depicted in FIG. 7 , may correspond to a thirteenth and a fourteenth slot respectively.
- a line card 20 b received by slot m 92 a may have a first front port 22 c and a first virtual port 44 a .
- another line card 20 c received by slot n 92 n may have a second front port 22 d and a second virtual port 44 b.
- an inter-card/intra-node link 42 a may be established between the first virtual port 44 a and the second virtual port 44 b over the backlink 34 .
- a first update module 76 a of a first state machine 24 b of a first line card 20 b may be operable to update the first state machine 24 b to an updated state based on a unit of state information.
- a second update module 76 b of a second state machine 24 c at a second line card 20 c may be operable to update the second state machine 24 c to the updated state based on the same unit of state information.
- the unit of state information may be provided to the two state machines 24 b , 24 c over the intra-node link 42 a .
- the unit of state information may be defined by a proprietary protocol.
- the unit of state information may be part of a pre-existing ring protection protocol.
- the unit of state information may be a state message 94 , such as, without limitation, any of the R-APS messages defined for ITU-T G.3082.
- a state message 94 may arrive at the first ring port 18 c .
- a first update module 76 a of the first state machine 24 b may update 96 the first state machine 24 b according to the ring protection protocol implemented by the ring 10 .
- a forwarding module 90 a residing on the first line card 20 b may forward the state message 94 .
- the state message 94 may be forwarded from the first front port 22 b to the first virtual port 44 a via the switch infrastructure 48 from the network interface 50 to the fabric interface 52 in a manner similar to any other frame/packet whose route involves the switch fabric 34 .
- the forwarding module 90 a may forward the state message 94 through the first virtual port 44 a and over the inter-card communication link 42 a supported by the backplane 34 to the second state machine 24 c residing on the second line card 20 c.
- the second update module 76 b of the second state machine 24 c may be designed to respond to the state message 94 received at the second virtual port 44 b according to the ring protection protocol as though the state message 94 were received at the second ring port 22 d .
- the second update module 76 b may update 98 the second state machine 24 c to the updated state.
- the first state machine 24 b and the second state machine 24 c may share a common state for the ring node 12 d - 2 .
- Another forwarding module 90 b and/or switch infrastructure 48 b at the second line card 20 c may then forward the state message 94 to the front port 22 d of the second line card 20 c serving as a ring port 18 d .
- the state message may then be forwarded to the next node 12 e to facilitate the coordinated implementation of the ring protection protocol as if the ring node 12 d - 2 with multiple state machines 24 b , 24 c , was a ring node 12 d - 1 with one state machine 24 a.
- Synchronizing multiple state machines 24 over an inter-card communication link 42 with state messages 94 used to coordinate a ring protection protocol across multiple nodes 12 a - f may lead to complications. For example, if there is a failure 100 of the inter-card communication link 42 a , state messages 94 , and other traffic can no longer be relayed across the ring node 12 d - 2 . To address such a failure 100 , a response may be required.
- One or more monitoring modules 88 may monitor the inter-card communication link 42 from the first virtual port 44 a of the first line card 20 b over the backplane 34 to the second virtual port 44 b of the second line card 20 c for a failure 100 .
- a monitoring module 88 may employ Continuity Check Messages (CCM), virtual port failure reports, and or other approaches to detect a failure somewhere along the inter-card communication link 42 a.
- CCM Continuity Check Messages
- one or more internal-port blocking modules 78 a , 78 b for the first state machine 24 b and/or the second state machine 24 c may block 102 , 104 a corresponding virtual port 44 , the first virtual port 44 a where an internal-port blocking module 78 a belongs to the first state machine 24 b and the second virtual port 44 b where an internal-port blocking module 78 b belongs to the second state machine 24 c .
- the first update module 76 a and the second update module 76 b may, respectively update the first state machine 24 b and the second state machine 24 c from an idle state to a new common state reflecting the failure 100 .
- one or more messaging modules 80 a , 80 b may send one or more failure messages 106 a , 106 b .
- a messaging module 80 a , 80 b on the first line card 20 b and/or the second line card 20 c may generate and send a failure message 106 a , 106 b out at least one of the two ring ports 18 c , 18 d of the ring node 12 d - 2 .
- Such a failure message 106 may indicate a need to open 32 an RPL 14 a blocked 16 to prevent a loop in a ring 10 of nodes 12 a - f to which the ring node 12 d - 2 pertains.
- a failure message 106 may be a message defined by the ring protection protocol to respond to a failure at a link 14 maintained between ring ports 18 of adjacent ring nodes 12 within a ring 10 defined by the ring protection protocol.
- a failure message 106 may be an R-APS Signal Fail (SF) message, R-APS(SF) message.
- SF R-APS Signal Fail
- directions of traffic may need to be altered, once the RPL 14 a is unblocked 32 , traffic can reach the various nodes 12 a - f in the ring 10 despite the failure 100 .
- a potential for a loop may arise while the RPL 14 a is unblocked 32 .
- transparency of the multiple state machines 24 may be achieved by differentiating roles played by the multiple state machines 24 in terms of their preventative actions.
- a set of master-role actions 82 may be performed by either the first state machine 24 b or the second state machine 24 c .
- a set of slave-role actions 84 may be performed by a state machine 24 b / 24 c not performing the set of master-role actions 82 .
- the set of master-role actions 82 may be assigned to the first ring-protection-protocol state machine 24 b or the second ring-protection-protocol state machine 24 c according to a predetermined convention.
- the set of master-role actions 82 may be assigned to a state machine 24 associated with the highest slot value.
- the set of slave-role actions 84 may be assigned to a state machine 24 with the lowest value.
- Other conventions are possible, and the foregoing convention may be reversed.
- slot n 92 b has the highest value and, therefore, the second state machine 24 c would be assigned the set of master-role actions 82 according to the first convention.
- the term set can include any number of elements and may include the null set.
- the set of master-role actions 82 may include blocking 110 a ring port 18 d corresponding to the state machine 24 c to which the master-role actions 82 are assigned in response to a recovery 108 of the inter-card communication link 42 b .
- the set of master-role actions 82 may block 110 a front port 22 d corresponding to a ring port 18 d before an internal blocking module 78 b unblocks 112 the corresponding virtual port 22 d in response to the recovery 108 of the inter-card communication link 42 b.
- the messaging module 80 b residing at the line card 20 c with the state machine 24 c assigned the set of master-role actions 82 may generate and send a link-up message 114 across the recovered inter-card communication link 42 b to prompt a state machine 24 b to unblock 116 a corresponding virtual port 44 a at a remote end of the inter-card communication link 42 b .
- the messaging module 80 b may generate the link-up message 114 after the blocking 110 of the corresponding ring port 18 d .
- the messaging module 80 b may generate the link-up message 114 by setting a Type, Length, and Value (TLV) option field of a CCM message to a predefined value.
- TLV Type, Length, and Value
- an internal-port blocking module 78 a residing at the line card 20 b with the state machine 24 b assigned the set of slave-role actions 84 , may unblock 116 the corresponding virtual port 44 a.
- a messaging module 80 a of the first state machine 24 b and/or a messaging module 80 b of the second state machine 24 c may send a recovery message 118 a , 118 b out the first font port 22 c serving as a first ring port 18 c and/or the second front port 22 d serving as the second ring port 18 d respectively.
- a recovery message 118 may be defined by the ring protection protocol to respond to a recovery of a link 14 maintained between ring ports 18 of adjacent ring nodes 12 a - f .
- the recovery message 106 may be an R-APS No Request (NR) message, R-APS(NR) message.
- the RPL 14 a may be blocked 16 in response to one or more recovery messages 118 .
- an indication 120 that the RPL has been blocked 16 may be required before the switch protection module 74 b /state machine 24 c assigned the set of master-role actions 82 unblocks 122 the front port 22 d serving as the corresponding ring port 18 d .
- the indication 120 may vary depending on a previously assigned ring-level role of the ring node 12 d - 2 .
- the switch protection module 74 b /state machine 24 c may wait for a restore clock 120 a to expire.
- the restore clock 120 a may be a Wait To Restore (WTR) clock.
- the switch protection protocol 74 b /state machine 24 c may unblock 122 the ring port 18 d maintained by the line card 20 c carrying the ring-protection-protocol state machine 24 c assigned the set of master-role actions 82 a.
- the switch protection protocol 74 b /state machine 24 c may wait to receive a blocking message, or root-blocked message 120 b , from the o ORPL node 12 a .
- the blocking message 120 b may be an R-APS Root Blocked (RB) message, R-APS (RB) message.
- the switch protection protocol 74 b /state machine 24 c may unblock 122 the ring port 18 d maintained by the line card 20 c carrying the ring-protection-protocol state machine 24 c assigned the set of master-role actions 82 a.
- the first update module 76 a and the second update module 76 b may, respectively, update the first state machine 24 b and the second state machine 24 c from their previous common state back to a shared idle state.
- the ORPL node 12 d - 2 / 12 a has blocked the RPL 14 a before unblocking 122 the ring port 18 d .
- Another opportunity for a loop can be avoided.
- the following figure provides a brief overview of ways in which loops may be avoided where a ring node 12 d - 2 is implemented with multiple state machines 24 .
- a ring protection system 10 progresses through various stages 10 a - c to prevent various potential loops.
- a first state 10 a the ring protection system 10 is depicted with the RPL 14 a blocked 16 , when a first event (1) occurs, namely a failure at 100 at an inter-card communication link 42 at a ring node 12 d - 2 that may be implementing multiple state machines 24 and may be utilizing the inter-card communication link 42 to transparently synchronize the multiple state machines 24 .
- the ring protection system 10 may then progress to a second stage 10 b at which the OPRL node 12 a and/or the neighbor node 12 b may have (2) unblocked 32 the RPL 14 a , potentially in response to one or more failure messages 106 , such that all links 12 a - f in the ring can be accessed despite the failure 100 .
- the inter-card communication link 42 may also (3) have been repaired 108 , and in accordance with the set of master-role actions 82 , the corresponding ring port 18 d may (4) have been blocked 110 to prevent a loop.
- the OPRL node 12 a and/or the neighbor node 12 b may have (5) blocked 16 the RPL 14 a .
- the switch protection protocol 74 b /state machine 24 c implementing the set of master-role actions 82 b may wait to (6) unblock 122 the ring port 18 d until it has received an indication 120 from the ORPL node 12 a that the RPL 14 a has been blocked 16 to avoid the potential for a loop.
- each block in the flowcharts may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s).
- each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
- these computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block-diagram block or blocks.
- These computer program instructions may also be stored in a computer readable medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block-diagram block or blocks.
- the computer program may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operation steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block-diagram block or blocks.
- a method 200 is depicted for determining whether to respond to a state message 94 .
- messages 94 with a node identification value matching that of a line card 20 receiving the message 94 may be discarded.
- those line cards 20 b , 20 c may share a common node identification value to assist in making them transparent.
- the presence of a common node identification value may occur from a paired line card 20 b / 20 c and may be important to synchronizing the pair of line cards 20 b , 20 c , as opposed to an indication that a message 94 has run its course. Therefore, the method 200 provides some examples of how a determination to respond to a message 94 in such an environment may be made.
- the method 200 may include receiving 200 a message 94 .
- a determination 204 may be made as to whether the message 94 has the same node identification value as the line card 20 receiving the message 94 . If the answer is NO, an update module 76 may make a determination 210 as to whether an update to the state machine 24 is required in light of the message 94 .
- the message 94 is a matched message 94 , which may be defined as a message 94 carrying a node identification value assigned to a node 12 providing the message 94 that matches a node identification value assigned to the line card 20 receiving the message 94 .
- a determination 206 may be made as to whether the message 94 was received from a corresponding virtual port 44 . If the answer is NO, the message 94 may be discarded 208 . In other words, if a matched message 94 arrives at the corresponding ring port 18 , the preservation module 86 may allow the matched message 94 to be discarded 208 without a response from the state machine 24 .
- the method 200 may proceed to the determination 210 as to whether an update to the state machine 24 is required in light of the message 94 . Regardless of the scenario under which the determination 210 is reached as to whether an update is required, the method 200 may 212 update the state machine 24 if the answer is YES. If the answer is NO, the method 200 may forward 214 the message 94 . In other words, the preservation module 86 may preserve the matched message 94 received at the virtual port 44 so that the update module 76 of the corresponding state machine 24 may determine whether 210 whether to update 212 the state machine 24 in response to the matched message 94 .
- a method 300 is depicted that (1) responds to a failure 100 on a link 42 that may be utilized to synchronize multiple state machines 24 residing at a common ring node 12 .
- the method 300 may also (2) prevent one or more loops after the previously failed link 42 is recovered 108 .
- the method 300 may include detecting 302 a failure 100 on the inter-card link 42 and blocking 304 one or more virtual ports 44 on either end of the link 42 in response. Additionally, the method 300 may involve sending 306 one or more signal failure messages 106 to coordinate implementation of the ring protection protocol within the corresponding ring 10 .
- a determination 308 may be made as to whether a recovery 108 may have occurred. If the answer is NO, the method 300 may return to sending 306 one or more fail messages 106 then, once again, to the recovery determination 308 . If the answer is YES, the method 300 may proceed to a determination 310 as to whether or not the method 300 is being implemented on a slot 92 at which the set of master-role actions 82 has been assigned.
- the method may wait to receive 312 a link-up message 114 .
- the corresponding virtual port 44 may be unblocked 314 / 116 .
- the method 300 may proceed by blocking 316 / 110 a front port 22 serving as a ring port 18 maintained by the line card 20 with the ring-protection-protocol state machine 24 assigned the set of master-role actions 82 upon detecting the recovery 108 , or shortly thereafter.
- the blocking 316 / 110 of a ring port 18 in response to a recovery 108 of the intra-node link 42 after a previous failure 100 may belong to the set of master-role actions 82 assigned to a given state machine 24 .
- the method 300 may proceed by unblocking 318 / 112 a corresponding virtual port 44 and sending 320 the link-up message 114 received 3312 at the other paired line card 20 at step 312 .
- a status, or recovery, message 118 may also be sent 322 to prompt a re-blocking 16 of the RPL 14 a .
- a determination 324 can also be made as to whether an indication 120 of re-blocking 16 obtains, which may be expiration of a restoration timer 120 a where the method 300 is implemented on an ORPL node 12 and which may be the reception of a root-block message 120 b where the method 300 is not.
- the method 300 may circle back to sending 322 the status/recovery message 118 and to the RPL-indication determination 324 . If the answer is YES, the method 300 may proceed to unblocking 326 / 122 the front port 22 serving as a ring port 18 , responding to the indication 120 that the RPL 14 a for a network ring 10 in which the corresponding state machine 24 participates has been restored 32 .
Abstract
Description
Claims (14)
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US9838215B2 (en) | 2017-12-05 |
WO2015047531A1 (en) | 2015-04-02 |
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